In current mobile communication networks, typically cellular mobile communication networks comprising a plurality of radio cells, subscriber identity modules are used within mobile stations, i.e. user equipments and/or MTC devices, comprising such subscriber identity modules. Currently, many subscriber identity modules are physically realized as hardware subscriber identity modules comprising a physical hardware interface (e.g., “contact pads”), a memory as well as a processor (e.g., “microcontroller” or “microprocessor”). Alternatively, so-called “soft SIMs” (software-based subscriber identity modules) can be used. In any case, subscriber identity modules within mobile stations such as user equipments and/or MTC devices can be regarded as necessary in the context of current mobile communication networks. Currently, each subscriber identity module has an assigned IMSI (International Mobile Subscriber Identity) and an assigned MSISDN (Mobile Subscriber Integrated Services Digital Network Number). In case that the assigned IMSI and/or the assigned MSISDN is or are identical for a plurality of subscriber identity modules, such subscriber identity modules are also called cloned subscriber identity modules.
In a GSM-based (Global System for Mobile communication) communication network, it is possible to clone SIM cards, so that each cloned card has exactly the same IMSI and MSISDN, an example thereof can be found in European patent publication EP 0 669 774 A1. Such cloned SIM cards (or cloned subscriber identity modules) can be given, e.g., to the same subscriber for usage in several devices in parallel or the operator (of the mobile communication network) could use cloned SIM cards (cloned subscriber identity modules) for usage in several different devices at the same time to save resources and costs. The latter can be described as pooling of cloned SIMs (cards) for specific usage scenarios, whereby it is important to save resources (used number of IMSIs and MSISDNs) and costs, which depend on the number of different subscribers in use.
Pools of cloned SIM cards are helpful, if, on the one hand, thousands or even millions of SIM cards are required, like for devices used for machine-to-machine communication, and, on the other hand, each device is only attached for a limited time to the mobile network. This could be a onetime attach to the mobile network or a periodic attach with an important time offset, such as attachment times of a few seconds or about 10, 20 or 30 seconds once every 24, 48, 72 hours or a few days, one or a few weeks, i.e. duty cycles of the order of magnitude of 1E-4, 1E-5 or even 1E-6.
Machine type communication is increasingly used in cellular mobile communication network, as well as in information and telecommunications systems in general. Examples of systems using MTC devices for MTC operations may include:
remotely controlled power meters as well as metering machine type communication devices,
remotely controlled machine type communication devices for controlling functions e.g. in a home which make it possible to turn on an heating prior to arriving home.
In addition to such examples of stationary machine type communication, there are also applications of mobile machine type communication, such as remotely monitoring and/or controlling functions or status information in a car, boat, or some other kind of vehicle.
A significant increase in signaling traffic and in data traffic in cellular access systems can be expected due to the vast amount of possible applications for MTC, MTC devices and MTC systems.
An MTC device may be connected through cellular access networks to mobile communication networks, the access networks may include GSM (Global System of Mobile Communication) access networks, GPRS (General Packet Radio System) access networks, and/or EPS/LTE (Evolved Packet System/Long Term Evolution) access networks. Typically, a MTC device will have relatively low mobility, low data consumption and infrequent communication. In addition, many, if not most, types of applications of machine type communication will be delay tolerant, i.e. they will not be real time applications, as opposed to traditional applications of cellular access networks, such as speech, streaming of data etc. In many cases, the application in which a MTC device is used needs the MTC device to report data, or it may happen that the MTC server needs to transmit data to the MTC device.
Cloned SIMs (or sim cards) could, e.g., be used for any kind of meter, like electricity or heating meter, which do not need a permanent access to the mobile communication network, but push the latest figures to a central server only once a day or once a week or the like.
However, the drawback of the use of such pools of cloned SIM cards is that collisions between cloned subscriber identity modules can occur, when the cloned subscriber identity modules (SIM cards) attach to the mobile core network at the same time (i.e. the corresponding user equipment or MTC device, comprising the cloned subscriber identity module, tries to be attached to the mobile communication network). Such collisions will lead to service outage or service degradation. In the worst case the collision could even end in a deadlock situation for (all or part of) the involved SIM cards. Currently, the only possibility to lower the collision probability is to limit the size of each pool of cloned SIM cards, but this limits also the benefit of cloning SIM cards
Currently, the core network does not support any means to resolve collisions, when a cloned SIM card tries to attach to the mobile network and one of its clones is already attached to the network. The last attach procedure would either supersede the connection of prior connected SIM card or the connection of both SIM cards might be ambiguous and not reliable.
This possibility that such a collision occurs is increasing with the number of transactions per cloned card and the number clones in the pool (or group of cloned subscriber identity modules). Therefore the usage of cloned SIM cards is limited to scenarios, where only a onetime access of the device containing the cloned SIM card is necessary or where at least the time interval between each attach procedure to the mobile network is long enough. Furthermore the size of the pool is limited as well.